Helen Epstein is an independent consultant and writer specializing in public health in developing countries, and an adjunct assistant professor at the Columbia University School of International and Public Affairs.In December 1993, a slum landlord in Baltimore named Lawrence Polakoff rented an apartment to a twenty-one-year-old single mother and her three-year-old son, Max.1 A few days after they moved in, Max’s mother was invited to participate in a research study comparing how well different home renovation methods protected children from lead poisoning, which is still a major problem endangering the health of millions of American children, many of them poor.

Amy L. Fairchild is a professor and the author, most recently, of “Searching Eyes: Privacy, the State, and Disease Surveillance in America.” David Merritt Johns is a journalist and doctoral student. Kavita Sivaramakrishnan is an assistant professor and author of “Old Potions, New Bottles: Recasting Indigenous Medicine in Colonial Punjab.” All are with the Center for the History and Ethics of Public Health Columbia University’s Mailman School of Public Health.In September of 1873, United States Senator J.R. West of Louisiana received a telegram from his home state whose terse lines spoke of abject desperation:The people are panic-stricken. All that could have left. The poor are nearly all on our hands; no money in the city treasury. All pecuniary aid will be thankfully received. Fever increasing.(Signed) Samuel Levy, Mayor...